Tag Archives: geology

The Wreck of the Farallon

by kaweah

Under the grey deep, the plains, canyons, peaks,
the flooded floor of the world rolls on to Laurentia,
pressing on the Farallon, plank, mast, and sail
out ahead on a black stone wave,
driving her under the buoyant earth,
caught in the undertow of her
sunken bow, sinking deeper,
ever deeper under the world,
compressed and cooked, her wet soul bleeds out,
hot and convecting, boils stone,
hollows out Pluto’s chambers,
mothers strata of generations
of volcanic boils, dead, young, and dying,
trembling in the California sun.

When the great sea-world strikes the land,
the submarine ridge is crushed,
her mid-seam ripped ajar,
her bow pulled into the earth,
stern slammed into the continent’s edge;
all the wreckage tangled in a heap.

Here and there, the demolition done,
the old world digested, the continental belly
heaves up; Pacifica, Laurentia knock and shear
in their tectonic intercourse; mountain roots
severed and sucked off in the wake,
the subterranean bone of dead volcanoes floats up,
breaks through the surface; and seaward, bits of bone
shattered and blended with the sea-bottom
sediments of eons, and mother’s clotted blood.

© 2016 Kaweah

A Drive to Oregon

by kaweah
Point Arena Light

Point Arena Light

For Thanksgiving Break 2015, the kid and I drove up the coast and through the Klamath Mountains to the Willamette Valley to visit Grandma, and from thence back through the Klamaths down to Mount Shasta and McCloud. We stayed the last night of the trip in a nice room above the shops in McCloud, and had dinner at a quaint, local pizza joint. McCloud struck me as a candidate for retirement, though perhaps not the best place to spend one’s final, feeble years.

Along the way, we stopped to see the sea-granite of Bodega Head, Point Arena, the coast redwoods of the Lady Bird Johnson Grove and Prairie Creek Redwoods State Park, plus a herd of Roosevelt elk crossing the highway.

For some unnumbered years I have been interested in the kinship between the Klamath Mountains and the Sierra Nevada. They seem to have been born together, split apart around Redding, California, and then pursued separate fates.

© 2015 Kaweah

The Last Gypsy of the Brennica

by kaweah

Here, young stranger, a speckled egg
of Carpathian granite, blooming with crystal,
stolen in my youth from the womb
of a Moldavian stream, said the old Gypsy
when he handed the riverstone to me.

Mill it—down to flour.
Fertilize it with this old man’s ash,
carry the meal up to Ram Mountain
and cast it out there. Like the Roma,
let the rain wash it to the Odra and the Wisła,
let that blend of stone and man
leaven the two waters
with the ashes of my love
and the soul of my mountains.

Let it ride the Wisła east, the Odra west,
Down through Silesia, past Krakow’s poet-tomb;
May it seal the wounds of my people,
Prussian and Pole, Czech and Jew—
children of the two veins together;
our dark blood never spill again
even to where the twin rivers spill
upon the northern sea.

© 2015 Kaweah

The Advent of Stone

by kaweah

a trap so baited was laid to catch you when the world began, before the granite foundation [1]

Before the granite was bedded to build the world on [2]

age-reddened granite that was the world’s cradle [3]

One of the themes that appeared in earnest when Robinson Jeffers published Tamar and Other Poems was the stone theme (hawks and eagles didn’t really appear until Cawdor, three releases and four years later). Tamar was published with shorter poems with titles like “To the Rock …” and “To the Stone-Cutters.” The next release, Roan Stallion, began with the poem “Granite and Cypress.”

Stone, for Jeffers, tended to mean granite, and even more specifically sea-granite [4], his term for the exotic granite that pushed up through the marine rock west of the San Andreas Fault. Before the Jefferses purchased those 16 lots at Carmel Point in 1919 [5], it is debatable whether stone ever meant very much to the poet.

Granite is not the dominant bedrock of Carmel-by-the-Sea or of the Central California coast in general. The coastal zone is west of the San Andreas Fault, and so its bedrock is primarily marine in origin. There are, however, exposures of granite throughout the coast of Central California. This granite is exotic to the terrain, as granite is not a marine rock. It is believed to have been sliced off of the Sierra Nevada Batholith many million years ago and moved slowly up the coast along the San Andreas Fault. Thus there is an outcrop of Sierra sea-granite at Carmel Point, and stone throughout Jeffers’s life work.

 

[1] Tamar (CP 1:38)
[2] Tamar (CP 1:54)
[2] Tamar (CP 1:80)
[3] Term used in The Cycle (CP 1:14) and Meditation on Saviors (CP 1:398)
[4] National Park Service, Historic American Landscapes Survey, HALS No. CA-56

In Geologic Times

by kaweah

Not so long ago,
I came upon Half Dome
half done, shrouded
in oak scaffolding.

Squinting my eyes,
I noted stocky little men
on the network of hardwood
toothpicks
with rosy cheeks and
beards like their bellies,
some chiseling away at the granite,
some polishing.

Looking again at all that
scaffolding, I recalled
how spacious the forests
and the meadows had been
before the white rangers came
and saved everything, and then
I thought, well,
these guys did it!

But what about the glaciers,
I inquired of one of the little people
who’d come by to offer me a pint.

What’s a glacier, he asked me.
Some kind of elf?

© 2013 Kaweah

 

California v. II

by kaweah

… continued

Metamorphosis

About thirty million years ago, the trailing edge of the Farallon Plate began to disappear under North America in the shape of an inverted 90° wedge, beginning at the location of present-day Los Angeles, and proceeding northeast under the continent, leaving nothing but hot mantle where before was the cold, subducting oceanic plate.

Burial of the Farallon Plate

Burial of the Farallon Plate

Over the past twenty million years, that trailing edge has been crossing the Sierra Nevada region, and it’s traveled nearly as far north as Mount Lassen thus far, creating a great triangle between the trailing wings of the subducted Farallon Plate and the Pacific Plate.

With no more subduction to trigger the kind of volcanic activity characteristic of Mount Lassen and the Cascade Range to the north, the Sierra Nevada has transitioned into a new phase of plutonic activity. The hot, underlying mantle has pressed up through the great triangle, causing uplift and, as the uplifted dome has increased the surface area above, spreading. The spreading, in turn, has created grabens such as Owens Valley.

Though the stone that makes the Sierra Nevada was formed long before this uplift and spreading, it was this event, beginning about thirty million years ago, that actually gave rise to the Sierra Nevada that we know today. Still, there have been much more recent events that have contributed greatly to the general, large-scale structure of the range.

A New Age of Volcanism

This new incarnation of California lacks the Cascadian volcanism of its past, yet the existence of the eruption of the Long Valley supervolcano 760,000 years ago attests to the volatility of the present-day Sierra Nevada. It was an eruption 500 times the size of the 1980 Mt. St. Helens eruption and 30 times the size of the 1883 Krakatoa eruption, surpassed by only four eruptions over the last million years:

  1. Lake Toba, Sumatra, Indonesia
  2. Whakamaru, North Island, New Zealand
  3. Lake Taupo, North Island, New Zealand
  4. Yellowstone Caldera, Wyoming, USA

There are no stratovolcanoes along the spine of the Sierra Nevada, but there is evidence of something more terrible.

Localized Foundering of the Farallon Plate

As the trailing edge of the cold, dense Farallon Plate was detached from the supporting mass of any trailing oceanic plate, that trailing edge must have begun to sink — not merely as a caboose follows a train downhill, but rather more directly down, as it was no longer supported on its western boundary.

Delamination and Mantle Drip

Such a sinking mass must have pulled on the lithosphere above it, and possibly pulled the dense root of the Sierra Nevada downward and away from the mountain range. Once the trailing edge of the subducted plate passed, the detached root of the Sierra — being relatively dense — may have begun to sink more directly into the depths of the mantle, causing local downwelling.

Subsidence east of Fresno

Sinking mountains east of Fresno

Asthenospheric mantle flowed in to fill the gap where the Sierra’s root had been — probably liquefying under reduced pressure, and the Sierra, without the ballast of its dense root, became more buoyant, and began to rise, pulling even more asthenospheric mantle up with it, some of which would have liquefied. As magma, it would have injected itself into cracks in and around the thin Sierra block, ushering in the current phase of Sierra volcanism.

As the delaminated Sierra root descends into Earth’s mantle, it has created a local convection cell. The sinking root is causing downwelling in its wake, and pushing mantle rock downward and outward ahead of it. This downdraft appears to be causing subsidence in the Tulare Basin and the western Sierra adjacent to the basin.

As the displaced mantle rock is pushed aside, it then begins to rise, creating upward pressure at its edges — probably more along one edge, due to asymmetry. The upward pressure creates a local updraft, which may be adding to the uplift of the Sierra.

Further Reading:

Active foundering of a continental arc root beneath the southern Sierra Nevada in California

Watching Whales in the Sink

California v. I

by kaweah

It’s common knowledge that water is the bane of fire, but the Earth tells us a different tale.

The continents of Pangaea

The continents of Pangaea

Up to about 200 million years ago, at the dawn of the Jurassic Period, there was no California. It might be said that even North America didn’t exist. North America had then part of the supercontinent of Pangaea, which was about to break apart.

As ancient peoples once imagined their world an island in a great sea, so Pangaea was an island in a great sea. For eons, the rivers of Pangaea carried sediments to that sea, loading down the dense, cool crust beneath the waters. That crust, it turn, was floating upon an ocean of lithospheric mantle, but the crust was getting heavier and losing its buoyancy, until finally it gave way, and began to list like a ship giving in to the sea.

Around Pangaea, ocean floors began to dive beneath it for the same reason, leading to what we know today as the Pacific Ring of Fire, and the Triassic supercontinent began to fracture under the strain of the spreading triggered by the suction of ocean floor subducting into its perimeter.

Here on the eastern shore of the great ocean, the Farallon Plate was born out of the disintegration of Pangaea. As this young oceanic plate dove under Pangaea (and later Laurasia), the uppermost layer of the plate was scraped off and piled against the edge of the continent, and so Cascadia was born. Cascadia is that land commonly known today as the Pacific Northwest. When California was young, it was part of Cascadia.

The continent was pulled westward and stretched along its margin, giving rise to the forearc basins known today as the Puget Sound, the Willamette Valley of Oregon, and California’s Central Valley.

The water-loaded serpentine hydrated the rock beneath the continent, liquefying the rock and causing streams of melt to form. This led to the formation of a volcanic arc along the Pacific Coast, and deep below, the plutons that would eventually uplift to become the Sierra Nevada and Klamath Mountains of the present.

The hydrated magma streams that feed the volcanoes of Cascadia are not pacified by their water continent, but contrarily, rendered all the more volatile by the resulting steam, making for explosive releases of subterranean fire, not unlike the sudden expansion of a grease fire when fed with water.

Down in Cascadian California, there was no San Andreas Fault, nor any great granitic Sierra Nevada. These and other characteristic features of present-day California would arise as the trailing edge of the Farallon Plate began to disappear under North America.

To be continued …

One Guy’s Macrocosm

by kaweah

I just had the pleasure of reading the first volume of Guy Murchie’s Music of the Spheres, titled The Macrocosm, and I can see that a lot has been learned about Earth, the Moon, and planets since I was born. Take this sectional illustration of Earth’s crust for example:

A rather outdated cross section of California

A rather outdated cross section of California

Note the complete absence of tectonic plates. Note that the Sierra Nevada is represented as a folded range, which it’s not. Furthermore, today we don’t think there’s a basalt layer beneath North America, and in fact, we don’t think there’s any root at all beneath the southern Sierra. That last bit has been discovered rather recently.

Continue reading →

Kissing the Killer

by kaweah
Nevada Fall (Ansel Adams)

Nevada Fall, Merced River

Throughout the lowlands singers sing
of your deep, feminine soul;
How reclining, you roll down your bed
amidst your veils and embankments;
They marvel at your fluent, accommodating ways,
how you slip through the world,
flowing around every obstacle,
rounding every edge, and
polishing every turn.

You compel us, it is true, down to where you lie.
Your eyes are limpid pools—it is true what they say,
and it is rumored far and wide that you mirror
the soul.

But the footing is treacherous around you. Your tender loam
gives way beneath our fingers and toes,
but your glistening bones are more hazard still.

It is true what men say, but I know you better yet.
I know you,
murderer.

The bones of old trees and bush
lie tangled in your arms.
I see your work.

Yesterday you might have been
merely a pool, and another, and another;
hung upon a sparkling, trickling necklace
virtually breathless and still
patient, accommodating
womb of a myriad, humming
vampires;
Algae multiplying,
colonizing your thickening blood.
The next day, you might be only lichen and bone.
Dry, white, crumbling bone, anchored deep within the earth—
or deeper still.
But now—
Now!

You gallop across mountains and vandalize
the sleepy canyons, tearing away the flesh and
leaving more bone drying in the sun,
your locomotive snarl,
your hissing, boulder-cracking roar!
Undulating waves, rolling and smacking,
sucking in air, mist storms exhaling!

Water the tyrant.
Water the destroyer—butcher, leveler,
Fury: skull-smashing and bone-snapping—sinew twisting;
Too murderously quick for suffocation; utterly

ruinous and
Beautiful kiss me.

Sisters of the Sierra

by kaweah

One special characteristic of the Sierra Nevada is that it’s a rare example of a high mountain range in a Mediterranean climate, which means that it is dry and sunny half the year and moist and mild during the other half of the year. This combination makes for a very combustible cycle of fuel production and fuel dehydration.

I’ve been looking for sister ranges of the Sierra Nevada; that is, other igneous ranges. What this means is that I’m looking for well-forested mountain ranges in Mediterranean climes. This generally means high mountain ranges, because altitude generally means two things: (1) orographic precipitation for production and (2) orographic lightning for combustion.

You’d think that the Andes where they cross the Zona Central of Chile would be an ideal example, but the Andes are rather sparsely forested in the northern half of the Zona Central, perhaps because the Andes are too lofty to the north for extensive forestation. South of here, in the Maule district (VII) and even more in the Biobio North district (VIII), there is more forest, but there is also more precipitation. Rain is in fact so common that it’s hard to call the climate Mediterranean. There is really no time of year that is truly dry in the southern half of the Zona Central; not, at least, as dry as most of California is in Summer.

There aren’t very many other choices, as far as I am aware. There are many lower Mediterranean ranges, and several high ranges near to Mediterranean climes, but not many high ranges are in Mediterranean climates.

The only others I know of are in Iran: the Alborz, Zagros, and Sabalan mountains. None of these is heavily forested, but in the case of Iran we can be quite confident that they were once more forested than they are today.

At present, though, I can think of no mountain range in the world that shares with the Sierra Nevada this Mediterranean annual cycle of production and combustion at a comparable scale.